Yes, she was a mature woman in her past life. But she lived a harsh and cruel life, where she didn't ever feel happy. She didn't know how it feels to be loved by someone. She never experienced it. She always assumed the worst thing not bcz she's dumb, but she just doesn't want to be hopeful. So I don't find it cringe whenever she act like a real child in her new life. It was her dream to have a family and be loved by everyone. The parts about her past life always makes me cry. The reason why she was isekai'ed also because she killed herself by having her body hitted by truck/bus. She did that bcz she said she never ever happy with her family, they are really evil and she wanted to make them feeling regret of her death. It revealed that she attempted many su*cide.

And apparently the new world she lived in is one of 100 world that created by herself. She's not a god, but the star keeper (?) made the unhappy souls to create the worlds (where people lived happiest/happily in it). The unfortunate/unhappy souls are called the dreaming child. They can create worlds bcz they longing somethings they can't have in their past life. But the FL doesn't have memory of it, she only have a memory of her life aka Cha Misoo's. It is sad how unfortunate she is, her life as Cha Misoo is really hurtful, and then when she died she can't rest peacefully and became a s*ave to create worlds.

MC soul is still incomplete and she's still alive in her previous world so her imprinting with dad is not complete but god will help her as she's is the one who created this world. There is a final villain of og world some starkeeper who manages sad broken children something like that.